1. Field of the Invention
The present invention relates to a semiconductor device and a manufacturing method thereof and particularly relates to a semiconductor device which controls a relatively large amount of electric power.
2. Description of the Related Art
In recent years, various kinds of products including integrated circuits have been produced in a variety of field, and increase in size and functionality of integrated circuits has increasingly progressed. While a circuit (a control circuit) for which high speed operation and/or low voltage operation is required is necessary for an integrated circuit included in a semiconductor device, a circuit (a power circuit) for which a sufficient reliability (high withstand voltage) is required at the time of high voltage application.
In general, elements included in an integrated circuit are formed using a silicon substrate. However, in recent years, an element which is formed using a semiconductor substrate which has a larger band gap than silicon has been attracting attention so that an element having higher efficiency for a power circuit is manufactured. For example, when silicon carbide (SiC) is used for an element for power source, the element formed using SiC has a dielectric strength voltage approximately ten times higher than an element formed using silicon and power loss can be drastically reduced when the element formed using SiC is used as an electric power converter such as an inverter or a converter; therefore, the element formed using SiC is expected to be put into practical use (for example, Patent Document 1).
For realizing practical use of a device formed using silicon carbide, defects of a silicon carbide substrate should be reduced. In general, a silicon carbide substrate formed using a sublimation recrystallization method tends to have hollow-core defects called micropipes and there is a problem in that even one micropipe in a transistor prevents the transistor from functioning. The size of a single crystal silicon substrate which is put into practical use is 12 inch. On the other hand, the size of a silicon carbide substrate is still 3 inch generally. Accordingly, when an integrated circuit which includes an element such as transistor formed using a silicon carbide substrate is manufactured, it is difficult to increase the size of the integrated circuit.
Further, there is a general tendency to create a trade-off between elements required for circuits (a control circuit, a power circuit, or the like) included in the integrated circuit; therefore, it is difficult for an integrated circuit with one semiconductor substrate to have multiple functions.
Reference
    [Patent Document 1] Japanese Published Patent Application No. 2003-229570